The present invention relates to a substrate for spawning mycelia into a compost and to the incorporation of proteins into composts.
In the cultivation of mushrooms, and particularly in the cultivation of Agaricus bisporus, commonly known as meadow mushroom, it is currently necessary to have nutrient substrates whereon the mycelium is sown.
In order to clarify the background of the problem, it is to be noted that mushrooms belong to the vegetable kingdom and, like almost all molds and bacteria, must be considered heterotrophic organisms that, since unable to produce organic substances directly from the mineral world, must resort to organic substances constituting other living organisms for their nutrition.
This type of metabolism imposes a dependent type of life, and therefore heterotrophic organisms can be considered saprophytes, parasites, or symbionts.
In the specific case at hand, cultivated mushrooms are saprophytes and therefore decompose organic substances of vegetable and animal origin in many different forms.
To grow mushrooms, it is therefore necessary to have a nutrient substrate, the choice whereof is restricted by economic factors and by the availability of the materials.
It is currently known to produce nutrient substrates essentially composed of cereal straw, fowl-dung, chalk, and water.
Cereal straw is the vegetable organic material that gives the compost adequate softness, whereas fowl-dung is the main source of nitrogen.
It is therefore known to mix and moisten these raw materials to promote spontaneous heating; the mass obtained is then mixed several times in the open air and placed in closed rooms, where fermentation and pasteurization are performed by adjusting parameters such as temperature and time.
The first compost degradation and transformation processes begin during fermentation and are performed by mesophilous and thermophilic microorganisms.
The pasteurization and conditioning step completes the biological and chemical processes that began during fermentation, and the purpose of pasteurization, which relies on a notable increase in temperature, is to eliminate residual parasitic forms arising during fermentation.
At the end of the conditioning step, the compost becomes selective and therefore suitable for sowing, said compost being placed beforehand in growing beds located inside greenhouses with a controlled microclimate.
This compost must be uniformly distributed throughout the thickness of the bed and on the surface thereof and must be supplemented with an additional protein source, usually soya.
The mycelium that covers the vegetable organic material subsequently becomes lanuginous and expands in the compost at a rate that depends not only on the cultivation system but also on the kind of mushroom and on the chemical and physical conditions of the compost.
It has been observed that in order to have a good production of mushrooms the nutrient substrate must be covered with a suitable soil, usually constituted by young or light-colored peat, black peat, and calcium carbonate.
This covering soil prevents the drying of the nutrient substrate, reduces temperature oscillations, and constitutes the support for the growth of the fruiting bodies; accordingly, it must be capable of absorbing the required amount of water, retaining it, and gradually releasing it.
Another characteristic of the covering soil is that it must maintain its structure even after being wet several times, and therefore must be soft, porous, and slightly coarse to allow adequate gas exchange within the beds and create a microclimate that favors the development of the mushroom, which begins with the accumulation of hyphae that join to form a very small pinhead-size spherical portion of tissue which is known as "primordium".
The primordium reaches the size of a pea after approximately one week, and the formation of the cap and of the stalk begins.
Under favorable conditions, it takes three days to pass from the pea stage to the stage of the normal, complete mushroom ready to be picked, although irregular growth patterns are observed in mushrooms.
Mushrooms are normally hand-picked when the cap is still closed, the tissue is firm, the rim of the cap is curved inwardly, the veil is intact, and the lamellae are not visible.
Going back to the analysis of the prior art, it is to be noted that the production process currently entails the initial production of the compost, its subsequent sowing with mycelium developed on caryopsides of cooked and sterilized rye, and the simultaneous introduction of a protein source, such as soya, which is prepared separately with organic acid and antiparasitic substances in order to prevent other molds from developing together with the mycelium.
This method of production has several drawbacks: first of all, the products are prepared with separate processes and therefore require resources, in terms of labor and means, that increase the overall cost of growing.
Furthermore, the additional protein source must be treated chemically, and this fact on one hand increases the cost of the final product and on the other hand leads to the possible presence of residual antiparasitic substances in the picked mushroom.
Finally, it is to be noted that this additional protein source added to a scarcely selective substrate is a source of nutrition for antagonist molds, which limit the normal development of the mycelium and sometimes suppress it.